/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize.peephole;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.editor.CodeAttributeEditor;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;

/**
 * This AttributeVisitor sets up and applies the peephole optimizations of its instruction visitor. The instruction
 * visitor should be using the same (optional) branch target finder and code attribute editor.
 *
 * @author Eric Lafortune
 */
public class PeepholeOptimizer extends SimplifiedVisitor implements AttributeVisitor {
    private final BranchTargetFinder branchTargetFinder;
    private final CodeAttributeEditor codeAttributeEditor;
    private final InstructionVisitor instructionVisitor;

    /**
     * Creates a new PeepholeOptimizer.
     * 
     * @param codeAttributeEditor the code attribute editor that will be reset and then executed.
     * @param instructionVisitor the instruction visitor that performs peephole optimizations using the above code
     *        attribute editor.
     */
    public PeepholeOptimizer(CodeAttributeEditor codeAttributeEditor, InstructionVisitor instructionVisitor) {
        this(null, codeAttributeEditor, instructionVisitor);
    }

    /**
     * Creates a new PeepholeOptimizer.
     * 
     * @param branchTargetFinder branch target finder that will be initialized to indicate branch targets in the visited
     *        code.
     * @param codeAttributeEditor the code attribute editor that will be reset and then executed.
     * @param instructionVisitor the instruction visitor that performs peephole optimizations using the above code
     *        attribute editor.
     */
    public PeepholeOptimizer(BranchTargetFinder branchTargetFinder, CodeAttributeEditor codeAttributeEditor,
        InstructionVisitor instructionVisitor) {
        this.branchTargetFinder = branchTargetFinder;
        this.codeAttributeEditor = codeAttributeEditor;
        this.instructionVisitor = instructionVisitor;
    }

    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}

    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) {
        if (branchTargetFinder != null) {
            // Set up the branch target finder.
            branchTargetFinder.visitCodeAttribute(clazz, method, codeAttribute);
        }

        // Set up the code attribute editor.
        codeAttributeEditor.reset(codeAttribute.u4codeLength);

        // Find the peephole optimizations.
        codeAttribute.instructionsAccept(clazz, method, instructionVisitor);

        // Apply the peephole optimizations.
        codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
    }
}
